Our strategy based on the analysis of CSF pulse pressure parameters seems to have a great accuracy in predicting surgical outcome in clinical practice.

The overall degree by which different patients may benefit from decompressive craniectomy (DC) remains controversial. In particular, the prognostic value of age has been investigated by very few studies. Many authors state there is no significant benefit in performing a DC in severe head injury after a certain age limit, with most placing the limit at 30-50 years of age. Between 1994 and 2004, 55 patients underwent DC at our institution. Advanced age did not constitute a contraindication to surgery for both ethical and cultural reasons. Thus, the data obtained were not biased by a selection of patients based on age. We analyzed potential predictors of outcome after DC, including sex, age, Glasgow Coma Scale (GCS), and presence of mass lesion. Chi-square test was used to compare categorical variables. The independent contribution of predictive factors to outcome was studied using logistic regression analysis. Initial GCS score was found to be an independent predictor of outcome (p = 0.001). No difference in the outcome was observed between patients with GCS 6-8 and GCS 9-15. These two groups have a better prognosis than patients with GCS 3-5. Logistic regression analysis showed age as an independent predictive factor to outcome (p = 0.005). A difference in outcome exists among patients over 65 and patients aged

A functioning shunt has an important impact on CSF circulation and pressure-volume compensation. Infusion studies can demonstrate the return of disturbed CSF dynamics to normal values even if clinical or radiological changes are not dramatic.

Object Apart from its mean value, the pulse waveform of intracranial pressure (ICP) is an essential element of pressure recording. The authors reviewed their experience with the measurement and interpretation of ICP pulse amplitude by referring to a database of recordings in hydrocephalic patients. Methods The database contained computerized pressure recordings from 2100 infusion studies (either lumbar or intraventricular) or overnight ICP monitoring sessions in patients suffering from hydrocephalus of various types (both communicating and noncommunicating), origins, and stages of management (shunt or no shunt). Amplitude was calculated from ICP waveforms by using a spectral analysis methodology. Results The appearance of a pulse waveform amplitude is positive evidence of a technically correct recording of ICP and helps to distinguish between postural and vasogenic variations in ICP. Pulse amplitude is significantly correlated with the amplitude of cerebral blood flow velocity (R = 0.4, p = 0.012) as assessed using Doppler ultrasonography. Amplitude is positively correlated with a mean ICP (R = 0.21 in idiopathic normal-pressure hydrocephalus [NPH]; number of cases 131; p < 0.01) and resistance to cerebrospinal fluid outflow (R = 0.22) but does not seem to be correlated with cerebrospinal elasticity, dilation of ventricles, or severity of hydrocephalus (NPH score). Amplitude increases slightly with age (R = 0.39, p < 0.01; number of cases 46). A positive association between pulse amplitude and increased ICP during an infusion study is helpful in distinguishing between hydrocephalus and predominant brain atrophy. A large amplitude is associated with a good outcome after shunting (positive predictive power 0.9), whereas a low amplitude has no predictive power in outcome prognostication (0.5). Pulse amplitude is reduced by a properly functioning shunt. Conclusions Proper recording, detection, and interpretation of ICP pulse waveforms provide clinically useful information about patients suffering from hydrocephalus.

In vivo shunt testing is easy, safe and clinically useful, aiding decision in difficult clinical situations, where shunt malfunction is suspected but not certain. It also has satisfactory positive predictive power.

A biphasic pattern of pulsatile intracranial pressure (pICP) was observed in all trials. Initially, until the CBF velocity remained constant, pICP increased (from 1.2 to 5.4 mmHg) following a rise in diastolic intracranial pressure (dICP); thereafter, in spite of a further rise in dICP, pICP decreased (2.87 mmHg) following CBF velocity reduction until intracranial circulation arrest (pICP=1.2 mmHg). A specular pattern was observed when the intraventricular infusion was stopped and CBF velocity returned to basal levels. These findings can be interpreted as indicating a hydraulic mechanism. Initially, when CBF is still constant, pICP rise is due to an increase in venous outflow resistance; subsequently, when CBF decreases following a further increase in venous outflow resistance, the vascular engorgement produces an arteriolar vasodilation. This vasodilation determines an increase in vascular wall stiffness, thus reducing pulse transmission to surrounding subarachnoid spaces.

Objectives The diagnosis of shunt malfunction is often not straightforward. We have explored, in symptomatic shunted patients with hydrocephalus or pseudotumour cerebri syndrome (PTCS), the accuracy of CSF infusion tests in differentiating a functioning shunt from one with possible problems, and the health economic consequences. Methods Participants: hydrocephalus/PTCS patients with infusion tests performed from January 2013 until December 2015. We followed patients up after 6 and 12 months from the test to determine whether they had improved, had persisting symptoms or had required urgent revision. We calculated the total cost savings of revision versus infusion tests and standard protocol of revision and ICP monitoring versus infusion tests. Results Three hundred sixty-five shunt infusion tests had been performed where a shunt prechamber/reservoir was present. For hydrocephalus patients, more than half of the tests (~55%, 155 out of 280) showed no shunt malfunction versus 125 with possible malfunction (ages 4 months to 90 years old). For PTCS patients aged 10 to 77 years old, 47 had possible problems and 38 no indication for shunt malfunction. Overall, > 290 unnecessary revisions were avoided over 3 years' time. Two hundred fiftyeight (> 85%) of those non-surgically managed, remained well, did not deteriorate and did not require surgery. No infections were associated with infusion studies. For Cambridge, the overall savings from avoiding revisions was £945,415 annually. Conclusions Our results provide evidence of the importance of shunt testing in vivo to confirm shunt malfunction. Avoiding unnecessary shunt revisions carries a strong health benefit for patients that also translates to a significant financial benefit for the National Health Service and potentially for other healthcare systems worldwide.

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